INFORMATION RELATIVE TO 
THE DRAFT TITLE V OPERATING PERMIT
September 2025

GENERAL FACILITY INFORMATION
Facility Name:  Southern Natural Gas Company LLC, Enterprise Compressor Station
Facility Address:  
100 County Road 332
Enterprise, MS 39330    
County: Clarke
SIC Code(s): 4922
NAICS Code(s): 221210  

APPLICATION SUMMARY 
Permit No.: 0440-00048
Permit Action:  Minor Modification
Permit Folder: PER20250001
Application Receipt Date: June 26, 2025
Application Deemed Complete: September 8, 2025
CBI Submitted?: No	NSPS (Part 60): Subpart KKKKa, Subpart JJJJ, Subpart OOOOb, Subpart A, Subpart GG
NESHAP (Part 61): N/A
NESHAP (Part 63): Subpart YYYY, Subpart ZZZZ, Subpart DDDDD, Subpart A
112(r) / RMP: N/A
Other: N/A	

FACILITY DESCRIPTION
Southern Natural Gas Company, LLC owns and operates its Enterprise Compressor Station located in Enterprise, Mississippi, for the purpose of transporting natural gas through its pipeline distribution system. The Enterprise Compressor Station will operate six (6) reciprocating compressor engines, four (4) emergency generators, two (2) compressor turbines, two (2) fuel gas heaters as well as insignificant activities. The following table includes all the significant emission points at the facility. All combustion units at the Enterprise Compressor Station are fired with natural gas.  The Enterprise Compressor Station is planning to install one stationary combustion turbine, one emergency generator engine, one fuel gas heater, a condensate storage tank, and add additional fugitives and blowdowns related to the new equipment. Two compressor engines (AA-003 and AA-004), one emergency engine (AA-012), and one fuel gas heater (AA-016) will be removed from service. 

The permit action is to modify the Title V Operating Permit, which will not trigger a Prevention of Significant Deterioration (PSD) Review.

Emission Point	Description	
AA-005	2,500 HP Cooper Bessemer GMVH-12C 2SLB SI natural gas-fired non-emergency compressor engine (Ref. No. 001C-010)	
AA-006	3,920 HP Cooper Bessemer 8W330-C2 2SLB SI natural gas-fired non-emergency compressor engine (Ref. No. 001C-011)	
AA-007	3,920 HP Cooper Bessemer 8W330-C2 2SLB SI natural gas-fired non-emergency compressor engine (Ref. No. 001C-012)	
AA-008	3,920 HP Cooper Bessemer 8W330-C2 2SLB SI natural gas-fired non-emergency compressor engine (Ref. No. 001C-013)	
AA-009	567 HP Caterpillar G3412 TA four stroke rich burn (4SRB) SI natural gas-fired emergency generator engine (Ref. No. 002G-003)	
AA-010	4,730 HP Caterpillar G3616 four stroke lean burn (4SLB) SI natural gas-fired non-emergency compressor engine equipped with an oxidation catalyst (Ref. No. 001C-014)	
AA-011	4,730 HP Caterpillar G3616 4SLB SI natural gas-fired non-emergency compressor engine equipped with an oxidation catalyst (Ref. No. 001C-015)	
AA-013	10,350 HP (61.2 MMBTUH) Solar Taurus T-70 natural gas-fired compressor turbine	
AA-014	650 HP Kohler 400 REZXB 4SRB SI natural gas-fired emergency generator engine	
AA-015	0.25 MMBTUH Fuel Gas Heater	
 AA-017	1,035 HP Caterpillar G3512 4SRB SI EPA Certified natural gas-fired emergency generator engine	
AA-018	A 23,369 hp, 165.38 MMBTU/hr non-emergency simple cycle natural gas compressor turbine	
AA-019	2,264 HP Caterpillar G3516 4SLB SI EPA Certified natural gas-fired emergency generator engine	
AA-020	0.864 MMBTU/hr Direct Heat Catalytic Fuel Gas Heater	
AA-000	Plant-wide Equipment and Pipe Fugitive Emissions	

TITLE V SOURCE APPLICABILITY 
The facility’s potential-to-emit (PTE) exceeds the Title V major source threshold of 100 tons per year (tpy) for each of the following criteria air pollutants: NOX, CO, and VOCs. The facility’s potential-to-emit hazardous air pollutants (HAPs) exceeds the Title V major source thresholds of 25 tpy of total HAPs and 10 tpy for the following individual HAP – Formaldehyde.

Facility-Wide Potential-to-Emit Summary1
Pollutant	PTE Emissions
(tons/yr)	
PM10	46.01	
PM2.5	46.00	
Sulfur Dioxide (SO2)	3.28	
Nitrogen Oxides (NOx)	505.64	
Carbon Monoxide (CO)	340.17	
Volatile Organic Compounds (VOC)	186.78	
Total HAP 	85.86	
1 The PTE emissions reflect any emission limits or enforceable restrictions included in the proposed permit.

PREVENTION OF SIGNIFICANT DETERIORATION (PSD) APPLICABILITY

The facility is not one of the 28 categorical facilities listed in 40 CFR 52.21(b)(1)(i)(c)(iii); therefore, the PSD threshold for a major source is 250 tpy.  The facility has the potential to emit more than 250 tons per year of NOx and CO; therefore, the facility is considered a major stationary source. With the removal of Emission Points AA-003 and AA-004, the PTE of VOC will reduce to 186.78 tons/year.  There are no changes being requested in this action that would be subject to PSD permitting and this permitting action will not change the current PSD status of the facility.

FACILITY MODIFICATIONS AND/OR PERMIT CHANGES

The facility submitted a 502(b)(10) in October 2024 to install gas coolers on AA-010, AA-011, and AA-013 as well as additional auxiliary components of piping. The same 502(b)(10) included a 750 kW emergency generator (AA-017) that is subject to the requirements of 40 CFR 60, Subpart JJJJ. Those requirements are already captured in the existing permit for Emission Point AA-014. 

For this modification, the facility will install one stationary combustion turbine, one emergency generator engine, one fuel gas heater, a condensate storage tank, and add additional fugitives and blowdowns related to the new equipment. The new equipment will be subject to the requirements of 40 CFR 60, Subparts KKKKa, JJJJ, and OOOOb, and 40 CFR 63, Subparts YYYY and ZZZZ.

Two compressor engines (AA-003 and AA-004) will be removed from service.
One emergency engine (AA-012) has been removed from service. 
One fuel gas heater (AA-016) has been removed from service.

COMPLIANCE ASSURANCE MONITORING (CAM) APPLICABILITY
40 CFR Part 64 specifies the requirements for CAM.  The general applicability of this rule can be found in 40 CFR 64.2 and requires a Title V source to comply with the CAM requirements if all three of the following criteria are met for a pollutant-specific emission unit (PSEU):

1.	The unit is subject to an emission limitation or standard for a regulated air pollutant other than exemptions under 40 CFR 64.2(b)(1);
2.	The unit uses a control device to comply with the standard; and
3.	The unit has pre-control emissions exceeding Title V major source threshold.

The facility has equipment (Emission Points AA-010 and AA-011) with pre-control emissions exceeding the major source thresholds and uses a control device (Oxidation Catalyst) to comply with an emission limit or standard.  Emission Points AA-010 and AA-011 each utilize an Oxidation Catalyst to control CO and Formaldehyde emissions below Major PSD Source thresholds.  The CAM Plan is provided in Appendix C of the permit.  

For Emission Point AA-011, the CO and Formaldehyde monitoring required by NESHAP ZZZZ is acceptable monitoring for complying with CAM.

NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS (NESHAP) APPLICABILITY
The facility is a Major Source of Hazardous Air Pollutants (HAP) since the facility has the potential to emit more than 25 tons per year of total HAPs and 10 tpy of an individual HAP.

40 CFR 63 Subpart ZZZZ - National Emissions Standards for Hazardous Air Pollutants for Stationary Reciprocating Internal Combustion Engines
The Reciprocating Internal Combustion Engines (RICE) NESHAP, Subpart ZZZZ, regulates HAP emissions from RICE.

Emission Points AA-005 through AA-008 are existing non-emergency spark ignition two stroke lean burn (2SLB) stationary RICE with a site rating of more than 500 brake HP located at a major source of HAP emissions and as such are not required to meet the requirements of 40 CFR Part 63, Subpart ZZZZ or the General Provisions in Subpart A.

Emission Point AA-009 is an existing emergency stationary RICE with a site rating of more than 500 brake HP located at a major source of HAP emissions.  As such, the emergency engine is only required to meet the emergency operational requirements of 40 CFR Part 63, Subpart ZZZZ.

Emission Point AA-010 is an existing non-emergency spark ignition four stroke lean burn (4SLB) stationary RICE with a site rating of more than 500 brake HP located at a major source of HAP emissions and as such is not required to meet the requirements of 40 CFR Part 63, Subpart ZZZZ or the General Provisions in Subpart A.

Emission Point AA-011 is a new non-emergency SI 4SLB stationary RICE with a site rating of more than 500 brake HP located at a major source of HAP emissions and as such is required to meet the requirements of 40 CFR Part 63, Subpart ZZZZ and the General Provisions in Subpart A.

Emission Points AA-014, AA-017 and AA-019 are new emergency generators, as defined in Subpart ZZZZ (40 CFR 63.6590(a)(2)(i)), with rated powers of 650 hp, 1,035 hp and 2,264 hp respectively located at a major source of HAP emissions that do not operate or are not contractually obligated to be available for more than 50 hours per calendar year for the purposes specified in 40 CFR Part 63.6640(f)(4)(ii) and as such are not required to meet the requirements of 40 CFR Part 63, Subpart ZZZZ or the General Provisions in Subpart A, except for the initial notification requirements, which have been met.

40 CFR 63 Subpart DDDDD - National Emission Standards for Hazardous Air Pollutants for Industrial, Commercial, and Institutional Boilers and Process Heaters 
Since the Enterprise Compressor Station is a “Major” source of Hazardous Air Pollutant (HAP) emissions, the facility is subject to 40 CFR 63, Subpart DDDDD.    

Emission Point AA-015 is an existing process heater in the “units designed to burn gas 1 fuel” subcategory as listed in 40 CFR 63.7499(l) and defined in 40 CFR 63.7575.  This unit does not have any applicable emission standards and only has to comply with the work practice standards of 40 CFR 63, Subpart DDDDD.  Emission Point AA-015 must have a tune-up completed every 5-years.  

The last 5-year tune-up of Emission Point AA-015 was conducted November 14, 2025.

Emission Point AA-020 is a new catalytic process heater. Catalytic heaters are flameless, therefore Emission Point AA-020 is not subject to the provisions of 40 CFR 63, Subpart DDDDD. 

40 CFR 63 Subpart HHH 
The NESHAP for Natural Gas Transmission and Storage Facilities establishes emission limitations and operating limitations for HAP emissions from applies to owners and operators of natural gas transmission and storage facilities that transport or store natural gas prior to entering the pipeline to a local distribution company or to a final end user, and that are major sources of HAP emissions.  The Enterprise Compressor Station does not operate any glycol dehydrators; therefore; NESHAP HHH does not apply to the facility.

40 CFR 63 Subpart YYYY 
The NESHAP for Stationary Combustion Turbines establishes national emission limitations and operating limitations for HAP emissions from stationary combustion turbines located at major sources of HAP emissions, and requirements to demonstrate initial and continuous compliance with the emission and operating limitations.  For purposes of NESHAP YYYY, a stationary combustion turbine is existing if construction or reconstruction of the stationary combustion turbine was commenced on or before January 14, 2003. A change in ownership of an existing stationary combustion turbine does not make that stationary combustion turbine a new or reconstructed stationary combustion turbine. A stationary combustion turbine is new if construction of the stationary combustion turbine was commenced after January 14, 2003.  

Emission Point AA-013 was constructed prior to the 2003 effective date and was relocated from an existing facility to the Enterprise Compressor Station in 2013.  However, relocation does not qualify as reconstruction.  Therefore, NESHAP YYYY does not apply to Emission Point AA-013.

Emission Point AA-018 is a new stationary combustion turbine that is constructed after January 14, 2003. Therefore, 40 CFR 63, Subpart YYYY applies to Emission Point AA-018. 

NEW SOURCE PERFORMANCE STANDARDS (NSPS) APPLICABILITY

40 CFR 60 Subpart GG
The provisions of 40 CFR 60 Subpart GG - New Source Performance Standards for Stationary Combustion Turbines are applicable to stationary gas turbines with a heat input at peak load equal to or greater than 10 MMBTUH, which commenced construction, modification, or reconstruction after October 3, 1977.  Emission Point AA-013 is rated at 61.2 MMBTUH, was constructed in 2002 and was relocated from an existing facility to the Enterprise Compressor Station in 2013.  Therefore, the facility is subject to the requirements of NSPS GG.

Emission Point AA-018 is a stationary gas turbine with a heat input at peak load equal to or greater than 10 MMBTU per hour. However, Emission Point AA-018 is regulated under Subpart KKKKa. Turbines that are regulated under Subpart KKKKa are exempt from the requirements of 40 CFR, Subpart GG. Therefore, Emission Point AA-018 is not subject to the requirements of Subpart GG. 

40 CFR 60 Subpart KKKK
The provisions of 40 CFR 60 Subpart KKKK - New Source Performance Standards for Stationary Combustion Turbines are applicable to stationary combustion turbines with a heat input at peak load equal to or greater than 10.7 gigajoules (10 MMBtu) per hour, based on the higher heating value of the fuel, which commenced construction, modification, or reconstruction after February 18, 2005.  

Emission Point AA-013 was constructed in 2002 and was relocated from an existing facility to the Enterprise Compressor Station in 2013.  However, relocation does not qualify as reconstruction.  Therefore, NSPS KKKK does not apply to Emission Point AA-013.

Emission Point AA-018 is a stationary combustion turbine with a heat input at peak load equal to or greater than 10 MMBTU per hour which commenced construction, modification, or reconstruction after February 18, 2005. However, Emission Point AA-018 will be constructed after December 13, 2024. Therefore, 40 CFR 60, Subpart KKKK does not apply to Emission Point AA-018.

40 CFR 60 Subpart KKKKa
The provisions of 40 CFR 60 Subpart KKKKa - New Source Performance Standards for Stationary Combustion Turbines are applicable to stationary combustion turbines with a heat input at peak load equal to or greater than 10.7 gigajoules (10 MMBtu) per hour, based on the higher heating value of the fuel, which commenced construction, modification, or reconstruction after December 13, 2024.

Emission Point AA-018 is a stationary combustion turbine with a heat input at peak load equal to or greater than 10 MMBTU per hour which commenced construction, modification, or reconstruction after December 13, 2024. Therefore, NSPS KKKKa applies to Emission Point AA-018.

40 CFR 60 Subpart IIII
The provisions of 40 CFR 60 Subpart IIII - New Source Performance Standards for Compression Ignition Internal Combustion Engines (NSPS IIII) are applicable to stationary compression ignition internal combustion engines that commenced construction, modification, or reconstruction after April 1, 2006.  None of the compressor station’s engines are compression ignition internal combustion engines, therefore, none of the compressor station’s engines are subject to any requirements of NSPS IIII.  

40 CFR 60 Subpart JJJJ
The provisions of 40 CFR 60 Subpart JJJJ - New Source Performance Standards for Stationary Spark Ignition Internal Combustion Engines (NSPS JJJJ) are applicable to stationary spark ignition internal combustion engines that commenced construction, modification, or reconstruction after June 12, 2006.  Emission Points AA-003 through AA-011 have not been constructed, modified, or reconstructed after the NSPS JJJJ effective date, therefore, these engines are not subject to any requirements of NSPS JJJJ.  

Emission Point AA-014 was manufactured in 2012. Therefore, the emergency engine is subject to the NSPS JJJJ emission standards for Emergency Engines Manufactured after 1/1/09 of:  NOx 2.0 g/BHP-HR 160 ppmvd@15% O2, CO 4.0 g/BHP-HR 540 ppmvd@15% O2, and VOC 1.0 g/BHP-HR 86 ppmvd@15% O2.

Emission Point AA-017 is a new 1,035 hp/750 kw emergency generator. Therefore, the emergency engine is subject to the 40 CFR 60, Subpart JJJJ emission standards for emergency engines.

Emission Point AA-019 is a new 4 stroke, spark ignition, lean burn engine with a maximum heat input of 15.01 MMBTU/hr and a rated power of 2,264 hp. Therefore, the emergency engine is subject to the 40 CFR 60, Subpart JJJJ emission standards for emergency engines. 

To demonstrate compliance with the emission standards in NSPS Subpart JJJJ, the facility purchased certified engines for Emission Points AA-014, AA-017, and AA-019. Therefore, no performance testing is required, but a maintenance plan must be followed, and records kept demonstrating that proper maintenance procedures are followed.

40 CFR 60 Subpart KKK
The provisions of 40 CFR 60, Subpart KKK - Standards of Performance for Equipment Leaks of VOC from Onshore Natural Gas Processing Plants (NSPS KKK) apply to affected facilities in onshore natural gas processing plants that commences construction, reconstruction, or modification after January 20, 1984, and on or before August 23, 2011.  Since the Enterprise Compressor Station is not located at an onshore natural gas processing plant, as defined in 40 CFR 60.631, the Enterprise Compressor Station is not subject to NSPS KKK.

40 CFR 60 Subpart OOOO
The provisions of 40 CFR 60, Subpart OOOO - Standards of Performance for Crude Oil and Natural Gas Production, Transmission and Distribution (NSPS OOOO) are potentially applicable to owners and operators of onshore affected facilities that commence construction, modification, or reconstruction after August 23, 2011.  The only potentially affected sources at the Enterprise Compressor Station are the facility’s compressor engines and oil condensate storage vessels.  However, the storage vessels are not new and have not been modified or reconstructed after August 23, 2011.  Further, none of the station’s RICE are located prior to the point of natural gas custody transfer.  Consequently, NSPS OOOO does not apply to the Enterprise Compressor Station.
40 CFR 60 Subpart OOOOa
The provisions of 40 CFR 60, Subpart OOOOa - Standards of Performance for Crude Oil and Natural Gas Facilities for which Construction, Modification or Reconstruction Commenced After September 18, 2015 (NSPS OOOOa) are potentially applicable to new and modified sources in the oil and gas industry after August 18, 2015.  The only potentially affected sources at the Enterprise Compressor Station are the facility’s compressor engines, with respect to Leak Detection and Repair (LDAR), and pneumatic controllers.  However, there have been no new compressors installed at the facility resulting in increased compression, nor has the facility modified any existing compressor engines or pneumatic controllers; consequently, NSPS OOOOa does not apply to the Enterprise Compressor Station.

40 CFR 60, Subpart OOOOb
The provisions of 40 CFR 60, Subpart OOOOb—Standards of Performance for Crude Oil and Natural Gas Facilities for Which Construction, Modification, or Reconstruction Commenced After December 6, 2022 are applicable to centrifugal compressors that are located within the Crude Oil and Natural Gas source category for which construction, modification, or reconstruction is commenced after December 6, 2022 (40 CFR 60.5365b(b)). The facility will have a new centrifugal compressor as well as new fugitives components. Therefore, the provisions of 40 CFR 60, Subpart OOOOb are applicable to the facility. 

SPECIFIC APPLICABLE REQUIREMENTS

Emission Point No.	Pollutant	Draft Permit Emission Limits	Monitoring Requirements	
AA-005 through
AA-008, AA-010, AA-011, AA-013,
AA-014, AA-017, and AA-019	PM	E = 0.8808*I-0.1667	Record Type and Quality of Fuel Used	
AA-009,
AA-015,
 and  AA-020	PM	0.6 lbs/MMBTU	Record Type and Quality of Fuel Used	
AA-005	NOX	12.7 lb/hr and 55.6 tpy	Biennial performance tests	
AA-006, AA-007, and
AA-008	NOX	24.0 lb/hr and 105.0 tpy per emission source	Biennial performance tests	
	CO	15.0 lb/hr and 65.0 tpy per emission source	Biennial performance tests	
AA-010
and
AA-011	CO	3.65 lb/hr and 16.0 tpy per emission source	Annual performance tests	
AA-010 and AA-011	NOX	7.3 lb/hr and 31.97 tpy per emission source	Semiannual portable analyzer tests	
	VOC	4.43 lb/hr and 19.41 tpy per emission source	Inspections and Control Device Operations	
AA-010 and AA-011	Fuel Restriction	Natural Gas Only	Record Type and Quality of Fuel Used	
	Control Device Requirement	Must be operated at all times	Monitoring of operations	
AA-011	CO or Formaldehyde	Reduce CO emissions by ≥ 93% or limit formaldehyde to 14 ppmvd at 15% O2	Semiannual portable analyzer tests	
	General
Operating
Condition	Catalyst pressure drop ≤ 2 inches H2O and catalyst inlet temp. ≥ 450 oF and ≤ 1350 oF	Monitoring of operations	
	General
Operating
Condition	Continuous Compliance	Monitoring of operations	
	General
Operating
Condition	Minimizing Emissions	Monitoring of operations	
AA-009,
AA-014, AA-017, amd AA-019	Operating
Condition	Emergency operations	Monitoring of operations	
AA-013	Fuel Sulfur Content	≤ 0.8 percent by weight	Record Type and Quality of Fuel Used	
	NOX	STD = 0.0150((14.4)/Y) + F	Record Type and Quality of Fuel Used	
	Fuel Restrictions	Natural Gas Only, with sulfur content ≤ 20 grains/100 scf	Record Type and Quality of Fuel Used	
	CO	11.89 lb/hr and 45.14 tpy	Record Type and Quality of Fuel Used	
	NOX	9.77 lb/hr and 37.05 tpy	Record Type and Quality of Fuel Used	
	VOC	3.10 lb/hr and 11.75 tpy	Record Type and Quality of Fuel Used	
AA-014, AA-017, and AA-019	NOX,
CO, and 
VOC	2.0 g/bhp-hr NOx or 160 ppmvd @ 15% O2
4.0 g/bhp-hr CO or 540 ppmvd @ 15% O2
1.0 g/bhp-hr VOC or 86 ppmvd @ 15% O2	Purchase of Certified engine	
AA-015
	SO2	4.8 lbs/MMBTU	Record Type and Quality of Fuel Used	
AA-015
	General Operating Conditions	Perform Tune Ups	Monitoring of operations	
		Minimizing Emissions	Monitoring of operations	
AA-018	Formaldehyde	91 ppbvd or less at 15-percent O2	Monitoring and performance testing	
	NOX	15 ppm of NOX at 15 percent O2 or 150 ng/J of useful output (1.2 lb/MWh)	Monitoring and performance testing	
	SO2	Fuel Requirement	Recordkeeping	
AA-018	GHG and VOC	Volumetric Flow Rate	Recordkeeping	
	GHG and VOC	Seal Repair	Recordkeeping	
AA-000	Methane, VOC	Monitoring Requirement	Recordkeeping	
	Methane, VOC	Repair Requirement	Recordkeeping	

OTHER REQUIREMENTS:
N/A